3.5 week buff orpingtons

Would love to hear some educated guesses! This is my first time raising chicks. I have 5 Buff Orpingtons. 3 of them are larger with fluffy tail feathers like #1 in the pic. #2 has a similar larger body, but tail is shorter and not fluffy. #3 is smaller and has almost no tail. Also has much smaller, almost non-existant comb yet. Thoughts on sex? I'm learning so much from this forum!